Method of removing moisture from a web of material



Dec. 1, 1970 543,410

METHOD OF REMOVING MOISTURE FROM A WEB. 0F MATERIAL w. TRACHTENBERG Filed May 8, 1969 Q 9 V TEE 6 m B m T m m M M L M W INVENTOR.

AGENT United States Patent W 3,543,410 METHOD OF REMOVING MOISTURE FROM A WEB 0F MATERIAL William Trachtenberg, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed May 8, 1969, Ser. No. 823,041 Int. Cl. F26b 5/04 US. Cl. 3418 Claims ABSTRACT OF THE DISCLOSURE A method of removing moisture from a web of material that is being moved continuously through a liquid bath. Upon emerging from the bath a suction is applied to the web preferably at right angles thereto and to one or both surfaces thereof. A flow of air is then directed at one or both surfaces of the web preferably at an angle that is in opposition to the direction of movement of the Web to move any remaining moisture into the effective region of the suction. This method effectively dries a liquid-developed photoconductive sheet or web and can be used at high processing speeds without any degrading effects as to the fragile liquid-toned image(s).

FIELD OF THE INVENTION The invention relates to a method for removing moisture from a sheet or web of material and more particularly to a method for removing moisture from and thereby drying a web of protoconductive material that has been moved through a liquid developer.

DESCRIPTION OF THE PRIOR ART In the field of electrophotography, a latent electrostatic charge image can be developed by moving a sheet or web bearing the latent image through a liquid developer which contains charged particles of the proper polarity. On movement through the liquid developer, the particles are drawn to those areas on the sheet or Web that have a charge of opposite polarity to that of the particles. When the sheet or web of such material is removed from the liquid developer, it is necessary to remove any moisture or liquid both from the image and nonimage areas to effectively dry the sheet or Web. Inasmuch as the particles adhered to the sheet or web in the image areas are relatively fragile, that is, can easily be smudged or smeared by any force tending to dislodge the particles, the manner in which the web is dried is of paramount importance.

Heretofore, squeegee rolls have been used effectively to remove moisture from a web of material, such as paper, which has a relatively coarse surface texture. However, the use of such rolls cannot be used effectively when applied to a web of material, such as film base, because the surface texture is relatively smooth and if sufficient force is applied to effectively remove the liquid, then the toner particles forming the image are disrupted to the extent that the image is smudged and smeared. The drying of a web has also been attempted by means of a drying cabinet through which the web is moved and subjected to a flow of heated air to remove the moisture and thereby dry the web. However, a drying cabinet removes the moisture very slowly and, hence, the length. of the web path through the drier must be relatively long. Further, irrespective of the manner in which the web path might be arranged, the cabinet is both bulky and expensive to include as an integral part of an electrographic apparatus.

3,543,410 Patented Dec. 1, 1970 SUMMARY OF THE INVENTION The primary object of the invention is to provide a method of removing moisture from a web of material so as to effectively dry the web irrespective of the speed at which the web might be moved.

Another object of the invention is to provide a method of removing moisture from a Web of electrographic material such that the drying operation is completed without any degrading elfect on the fragile liquid-toned image.

Still another object of the invention is to provide a method of removing moisture from a web of electrographic material in which the operation can be completed in a very short period of time and with a relatively high rate of processing speed.

Other objects and advantages of the invention will be apparent to those skilled in the art from the detailed description which follows.

The objects of the invention are attained by first subjecting the moving web of material to a suction device or knife which is arranged in very close proximity to a surface of the web and which effectively removes about 60- 70% of the liquid on the surface. Subsequently, the web of material is moved with respect to an air knife comprising a curtain or flow of air that is directed against a surface of the web at an angle that is in opposition to the direction of movement of the Web. The angle at which the air knife is set relative to the Web of material will vary in accordance with the vertical angle of the web and its linear speed. The distance by which the suction knife and air knife will be separated is also dependent on the vertical angle and linear speed of the web of material. This distance must be such that the air knife blows any remaining moisture toward and within the effective area or range of the suction knife. Further, the suction knife and air knife can be arranged With respect to both surfaces of the web and with such an arrangement the web can be dried to within of the contained moisture. In instances where the method has been used with respect to a liquid-developed electrostatic material, such material can be moved at a rate of about 60 feet/ minute with removal of 95 of the moisture and without any damaging effects on the toned image.

DESCRIPTION OF THE DRAWINGS Reference is now made to the accompanying drawing wherein like reference numerals designate like parts and wherein:

FIG. 1 is a diagrammatic elevational view showing the path of a web of electrographic material and the relation of a suction knife and air knife relative to the web of material; and

FIG. 2 is a partial sectional view through a suction knife showing the relaitvely small aperture that is used for withdrawing the excessive moisture from the web of material.

DESCRIPTION OF THE PREFERRED EMBODIMENT While the invention is described hereafter with respect to an electrographic material, it is to be understood that the method or process disclosed and described hereinafter can be used with substantially the same results for removing moisture from and drying at web of material irrespective of its type or composition.

A web 10 of electrographic material has one or more latent electrostatic images arranged across and/ or longitudinally thereof on a surface 12. The web 10 is moved continuously in a well-known manner and brought into contact with a roll 13 by which the web 10 is partially immersed in a liquid developer 14 contained in a suitable receptacle 15. The web 10 emerges from the liquid developer and the surface 12 then contains a plurality of images 16 that are formed or defined by toner particles that have adhered to surface 12. Reference is made to US. patent application Ser. No. 739,326, filed June 24, 1968, in the name of William Tractenberg et al. in which several devices are disclosed for guiding a moving web of electrographic material through a liquid developer. Any one of these devices can be substituted for the roll 13 in the present disclosure.

After the web leaves the liquid developer, it is moved between a pair of suction knives designated by numerals 17 and 18. These suction knives are identical in structure and one such knife is disclosed in FIG. 2 as comprising plates 19 and 20 which are formed to provide a central cavity 21 and a narrow opening 22 that extends to the bottom thereof. A plate 23 is formed, as shown, and such a plate is attached to each of plates 19 and 20 by screws 24 the ends of plates 23 forming a relatively narrow slot or opening 25 extending along the bottom of knife 17. In their assembled relation the plates 19 and 20 are provided with at least one threaded aperture or hole 26 to which a vacuum source can be connected in a well-known manner. Knives 17 and 18 are, preferably, slightly longer than the web 10 is wide. As shown in FIG. 1, the suction knives 17 and 18 are arranged generally perpendicular to the plane of the web 10 and, preferably, are spaced about 0.015 to 0.030 inch from the facing surface of the web.

Spaced from suction knives 17 and 18- in the direction of web movement are a pair of air knives 30 and 31. The structure of these air knives can be substantially the same as that of the suction knives with an opening 25 of appropriate width and no further description is deemed to be necessary. The air knives 30 and 31 are connected to a source of compressed air and arranged at an angle of about 30-45 with respect to the surface of the web 10 and, preferably, with the angle in opposition to the direction of movement to the web. As stated hereinabove, a suction knife and an air knife can be used with respect to only one or to both surfaces of web 10.

After leaving the air knives 30 and 31 the web 10 passes over a roll 32 and then around a drum 33. Depending on the material that is being dried, the drum 33 can be provided with a heating unit or a flow of air can be applied to the surface of the web 10 at the roll 33, such as by a heat gun 34. At this point, the drying will be finalized and the operating temperatures of the drum 33 and/or gun 34 will depend on the linear speed of the web and on the amount of liquid still remaining on the surface or surfaces of the web after passing the suction knife. With respect to a photoconductive or electrographic material, the temperature will also be dependent on the composition of the web as well as the linear speed. This final application of heat will also fix the toned image to the surface of the electrographic material, if the toner is one associated with a heat-sensitive resin or binder.

As stated hereinabove an electrographic material can be satisfactorily dried with a movement of 60 feet/ minute with respect to a suction and air knife arranged as shown in FIG. 1. If a higher processing speed is used, more than one set of suction and air knives can be used and arranged with respect to each surface of the web. In this way a greater quantity of liquid developer would be carried off by the total action of the knives at the higher speed. In the case of a sheet of electrographic material, the suction and air knife combination could be mounted relative to one another such that they could be moved as a unit over a stationary sheet of material. Further, it is conceivable that this method of removing moisture is not necessarily related to the speed of the web relative to the suction and air knives or vice versa.

The invention has been described in detail with partic- 4 ular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. A method of removing moisture and drying a web of material movable through a liquid bath, the steps comprising:

applying a suction, extending transverse to the direction of movement of said web of material and located in close proximity to said liquid bath, for removing the moisture from at least one surface of said web of material; and subsequently directing a flow of air, extending transverse to the direction of movement of said web of material, toward at least said same one surface of said web of material for moving any remaining moisture into the effective suction range.

2. The method in accordance with claim 1 wherein said suction is applied generally perpendicular to the plane of said web of material.

3. The method in accordance with claim 1 wherein said flow of air is directed at an angle to the plane of said web of material and in opposition to the direction of movement of said web of material.

4. The method in accordance with claim 1 wherein at least one suction and at least one subsequent flow of air are applied to each surface of said web of material.

5. A method of removing moisture and drying a web of material movable through a liquid bath for developing the latent electrostatic images carried thereby, the steps comprising:

applying at least one suction, extending transverse to the direction of movement of said web of material and located in close proximity to said liquid bath, for removing the moisture from at least one surface of said web of material; and subsequently directing at least one flow of air, extending transverse to the direction of movement of said web of material, toward at least said same one surface of said web of material for moving any remaining moisture into the effective suction range.

6. The method in accordance with claim 5 including the step of directing an additional flow of heated air toward said one surface.

7. The invention in accordance with claim 5 including the step of heating said web of material subsequent to removal of substantially all of said moisture.

8. The method in accordance with claim 5 wherein at least one suction and at least one subsequent flow of air is applied to each surface 'of said web of material.

9. The method in accordance with claim 5 wherein said suction is applied generally perpendicular to the plane of said web of material.

10. The method in accordance with claim 5 wherein said flow of air is directed at an angle to the plane of said web of material and in opposition to the direction of movement of said Web of material.

References Cited UNITED STATES PATENTS 1,180,255 4/1916 Cossitt et al. 34-16 X 2,022,593 11/1935 Frykers 34-23 2,249,179 7/1941 Schur 34-18 1,861,918 6/1932 Hickman 34--16 2,492,974 1/1950 Dungler 34156 WILLIAM J. WYE, Primary Examiner US. Cl. X.R. 

